Variable area nozzle for gas turbine engines driven by shape memory alloy actuators

Abstract

A gas turbine engine includes a variable area nozzle having a plurality of flaps. The flaps are actuated by a plurality of actuating mechanisms driven by shape memory alloy (SMA) actuators to vary fan exist nozzle area. The SMA actuator has a deformed shape in its martensitic state and a parent shape in its austenitic state. The SMA actuator is heated to transform from martensitic state to austenitic state generating a force output to actuate the flaps. The variable area nozzle also includes a plurality of return mechanisms deforming the SMA actuator when the SMA actuator is in its martensitic state.

We claim:  
     
       1. A mechanism comprising: 
       a four bar linkage including a non-movable arm, an output arm, a flap and a link, each of the non-movable member and the output arm being coupled to both the link and the flap; and  
       a SMA actuator, including a deformable element, engaging said output arm, said SMA actuator generating a force output upon transition from a martensitic state to an austenitic state.  
     
     
       2. The mechanism according to  claim 1 , wherein said four bar linkage is a parallel four bar linkage such that the deformable element of said SMA actuator cooperates with the four bar linkage to cause the output arm to move substantially in a parallel direction relative to a direction of motion of the deformable element. 
     
     
       3. The mechanism according to  claim 1  wherein said four bar linkage is a non-parallel linkage such that the deformable element of said SMA actuator cooperates with the four bar linkage to cause the output arm to move substantially in a nonparallel direction relative to a direction of deformation of the deformable element. 
     
     
       4. The mechanism according to  claim 1  wherein the deformable element of said SMA actuator comprises an array formed from a plurality of SMA strands. 
     
     
       5. The mechanism according to  claim 1  wherein said SMA actuator has a first SMA end and a second SMA end with said first and second SMA ends being fixed. 
     
     
       6. The mechanism according to  claim 1  wherein the deformable element of said SMA actuator is a rope. 
     
     
       7. The mechanism according to  claim 1  wherein said SMA actuator is a rigid member.